American Wood Council Calculators and Tools

[jar546]

You might find this link extremely useful:

Calculators & Tools

awc.org

According to the AWC:

A 2x8 treated southern pine used as a floor joist can span 12'11" at 16"o.c. with a live load of 40psf and a dead load of 10psf in wet conditions. They also claim that this span only requires 5/8" of bearing on each end. This would be in compliance with a deflection limit of 1/360.

How does this compare with the code requirements of the IRC for the same application?

 

[steveray]

Off by about a foot...But the IRC is conservative....

 

[e hilton]

The part that surprises me is the 5/8” bearing.

 

[wwhitney]

The part that surprises me is the 5/8” bearing.

5/8" bearing at each end, and 1-1/2" member width = 1-7/8 in^2 of total bearing area.

50 psf total load * 16"/12" tributary width * 12' 11" span = 861 lbs total load.

861 lbs / 1-7/8 in^2 = 460 psi allowable compression load perpendicular to the grain, after all the design factors have been applied.

That's in the expected ballpark, depending on species the reference design value (before design factors have been applied) varies from 300 to 900 psi.

Cheers, Wayne

 

[e hilton]

How does this compare with the code requirements of the IRC for the same application?

2015 IBC 2308.4.2.2 the ends of each floor joist shall have not less than 1-1/2” bearing

 

[jar546]

2015 IBC 2308.4.2.2 the ends of each floor joist shall have not less than 1-1/2” bearing

Correct.